Carbon nanotubes have special structure and many superior chemical and physical properties, such as high thermal conductivity, high electric conductivity, high strength and lightweightness. Therefore, application of carbon nanotubes is developing prosperously, especially the composite material integrating a substrate with carbon nanotubes to add superior properties of carbon nanotubes to the substrate. For example, the composite materials integrating metallic materials, plastic materials, semiconductor elements or fabric fiber with carbon nanotubes have been extensively studies and widely used. Therefore, the composite materials containing carbon nanotubes are growing more and more important.
A Taiwan patent No. I448424 disclosed a method for fabricating a carbon nanotube composite material, which comprises steps: dissolving polyvinylidene fluoride (PVDF) in a first solvent to form a PVDF solution; providing a powder of carbon nanotubes, and dispersing the carbon nanotube powder in the PVDF solution to form a first suspensoid; moving the first suspensoid to a second solvent to segregate PVDF from the first solvent and let a portion of PVDF combine with the surface of carbon nanotubes so as to form a second suspensoid; filtering the second suspensoid to obtain an intermediate product; baking the intermediate product to form a carbon nanotube composite.
In fabricating a carbon nanotube composite, it is critical for the properties and quality of the carbon nanotube composite material to uniformly distribute carbon nanotubes in the substrate. In the conventional technologies of fabricating carbon nanotube composite materials, the mixing methods can be categorized into a wet type (e.g. the one used by the prior art described above) and a dry type. The wet type mixing method uses a liquid as the medium and uses mechanical force to mix carbon nanotubes with a substrate or another material. The dry type mixing method directly mixes carbon nanotubes with a substrate or another material in a dry state. However, there is always possibility of uneven mixing no matter what type of mixing method is used.